Sticker shock: air conditioner

[friz]

Originally Posted by smj

The best ac for cooling the boat that we have had was a Coleman rv rooftop model. It would cool our 38' catamaran down into the 60's on a humid 90 degree Texas summer afternoon. It was a little large on the deck, but they do make low profile models and even a marine unit now.
The second best was a window unit. Inexpensive, cooled well but did give it the ghetto ambiance. Who cares if your inside and comfortable.
Seemed to me the water cooled marine units were the most inefficient. In most places when it's hot outside the water is also hot. I'm sure they would be more efficient if your located in an area where the water is cooler. A couple of other things I didn't like about the marine units are it seemed the filter would always clog sometime between midnight and 6:00 am and I never felt comfortable running it when we were of the boat as I had a couple of friends that had the hose rupture and almost sank the boat. They do look nice and remain concealed though.

Thank you SMJ! I was about to ask about RV ACs. I have about 15' of deck forward of the flying bridge. Perfect for a RV AC. Happy to read yours works well. For me, all the other options have major drawbacks: cost, efficiency, appearance. Actually my cabin cruiser came to me as a trailer park cruiser. Stern sliding glass door access to the cabin had been removed. They were less than tastefully replaced with a piece of plywood and residential window AC covering half of the opening. The other half provided access to the cabin via a cut down house door, plywood and 2x4 frame. Have since located an original sliding glass door and frame but now want AC for here in Florida. As I understand from RV AC experience they are purely cooling units. Any heating function is covered by electric heat strips. I have read that pure ACs use a somewhat different cooling cycle than heat pump reverse cycle units making them more efficient.

[Tx J]

Originally Posted by friz

Thank you SMJ! I was about to ask about RV ACs. I have about 15' of deck forward of the flying bridge. Perfect for a RV AC. Happy to read yours works well. For me, all the other options have major drawbacks: cost, efficiency, appearance. Actually my cabin cruiser came to me as a trailer park cruiser. Stern sliding glass door access to the cabin had been removed. They were less than tastefully replaced with a piece of plywood and residential window AC covering half of the opening. The other half provided access to the cabin via a cut down house door, plywood and 2x4 frame. Have since located an original sliding glass door and frame but now want AC for here in Florida. As I understand from RV AC experience they are purely cooling units. Any heating function is covered by electric heat strips. I have read that pure ACs use a somewhat different cooling cycle than heat pump reverse cycle units making them more efficient.

Friz, (bolded text above) That is flat wrong.
A 'heat pump' (a 'reversing' AC) functions exactly as does a 'pure' AC in the cooling mode. Same refrigerant, same coils, tubing, even the same compressors.
Where a heat pump shines is in 'heating mode', when it is 3 to 4 times more efficient and powerful than the old standard 'heat strips' (think 'toaster'), which are pure electric resistance heating.

I know, sounds wrong. But here's a link to the Wikipedia "heat pump" page, and I'll quote some of it below to give the details.
With resistance heat strip heating, 1000 watts of input electricity gets you just about 1000 watts of heat output. A 1:1 ratio.
With heat pump heating, 1000 watts of input electricity gets you 3000-4000 watts of heat output. A 3-4:1 ratio, quite a gain.
A three to four times greater output for the same input. Can't beat that with a stick...

In short, heat pumps really are a superior AC unit, and usually only cost slightly more (for the slightly more complicated piping, controls, and the reversing valve itself.

Heat pump Wikipedia link:
https://en.wikipedia.org/wiki/Heat_pump

"Heat pumps are used to transfer heat because less high-grade energy is required than is released as heat. Most of the energy for heating comes from the external environment, only a fraction of which comes from electricity (or some other high-grade energy source required to run a compressor). In electrically-powered heat pumps, the heat transferred can be three or four times larger than the electrical power consumed, giving the system a coefficient of performance (COP) of 3 or 4, as opposed to a COP of 1 for a conventional electrical resistance heater, in which all heat is produced from input electrical energy."
...
"Reversible heat pumps work in either direction to provide heating or cooling to the internal space. They employ a reversing valve to reverse the flow of refrigerant from the compressor through the condenser and evaporation coils."

[ValiantV]

Having tried the "portable AC" route on my 30', I have to call it a failed experiment.

The fact is that if you have a single hose (exhaust) unit, the unit sucks inside (cooled) air through the condenser to cool it, then exhausts this air out through that one hose/duct.

How many CFM that is I can't speak to, but, that air HAS to get replaced or the occupants of the boat would die by being decompressed or the boat would collapse from the vacuum.

The "make-up" air comes in from outside. Whether that is through gaps around the companionway, a leaky hatch or who-knows-where depends upon your boat.

That incoming air is hot and humid. (Otherwise, why are you running an air conditioner?)

On the Gree unit I bought (cheap at Walmart) the amount of air blown out through the exhaust is substantial.

Perhaps on the DeLongi unit it's less. I can't say. I went with the Gree because the last portable Haier unit I bought failed just after the warranty period.

Anyway, on MY boat with a portable air conditioner, the results are less than acceptable. In 95F humid weather, you're lucky to get 5-10F of cooling with the unit running 24/7. The ONLY time the boat got comfortable is after sunset when the temp drops to 80 or less. Then, the make-up air is also cooler and less humid.

Since the portable AC was just a stop gap measure while I fix my REAL AC, I'll get over it. But this has been a valuable lesson about portable AC units.

Now, if I can find a way to build a "plenum" and insert the condenser half if the AC into it, and route a second duct to supply outdoor air to the condenser, this MIGHT be a workable solution.

Failing that, this has just inspired me to get on the stick and fix my boat's AC - or - buy a new one for $1,500 and install it.

Just be aware of how portable AC units work and their built-in limitations.

[Lake-Effect]

Originally Posted by taxwizz

WOW ! Where did you find that [8000BTU unit for $75]?
I want one too.

Princess Auto (Canada's answer to Harbor Freight).

Every so often they have an unannounced sidewalk sale where they blow off old stock, refurbished, remanufactured, etc stock, and the prices are usually astounding. This was allegedly 50% off their normal selling price.

We were there at the right time to buy something else, we saw the stack of AC units they were blowing off, we bought one. We lucked out, basically.

Even so, it seems that every store is starting to put their AC units on sale now. Back to school sales are in full swing. Next up, Christmas ads

[YARGESOL]

this thread is rising faster I can read it ((( Studied the previous CF opinions and, many positive votes for portablle AC , I went last year for the portable 14000 Sinclair unit (wasn't easy to find one like this). It's fixed in the salon with a duct running with a curve to /through the rear bulkhead. Adjusting it,I 've found it's very sensitive to the duct length and ,the curves.
The best would be 2-3 feet long,direct to the side portlight for the airflow. But, I don't think it a good idea to have 75Lbs unit loose in the boat with a loose hose...So,it's fixed. Yes, it cools. But, the rearside and the hose is exessively worm/hot. I rerplaced original plastic hose with insulated acustic duct. Now it's better.
This spring, I was trying to use it as a heater...but, the duct should be repositioned In/Out to make heat.
I also have a fixed watercooled Flagship AC - I think 16000btu. This "Made with pride!" unit is noisy like a bear,blows charts out of the table but, have troubles to cool.The reason maybe the water isn't cold,or that the pump runs on 50Hz instead of 60Hz - 20% waterflow. And, not able to start with my Panda. Only with 32 Amps/220V,or 50Amps/110V shore.
I'm about to go for the 3-d unit - to cool the aft cabins - I have a place to locate it with a short,direct ducting to the cabins. And , Dometic Turbo DTU 16 looks right (about $3K offers) ,plus the Smart Start. But, I have a fear to drop another $3K++ without any positive signs... Maybe othe CFM have used Slef Contained AC units?

[Scout 30]

What I'd like to know is what's the biggest marine ac unit that can be run by a Honda 2000? We were talking to a Rosborough dealer recently & he was installing the Coleman 9500 btu roof units because the Honda 2000 was able to run them.

[Outlaw7]

Originally Posted by YARGESOL

this thread is rising faster I can read it ((( Studied the previous CF opinions and, many positive votes for portablle AC , I went last year for the portable 14000 Sinclair unit (wasn't easy to find one like this). It's fixed in the salon with a duct running with a curve to /through the rear bulkhead. Adjusting it,I 've found it's very sensitive to the duct length and ,the curves.
The best would be 2-3 feet long,direct to the side portlight for the airflow. But, I don't think it a good idea to have 75Lbs unit loose in the boat with a loose hose...So,it's fixed. Yes, it cools. But, the rearside and the hose is exessively worm/hot. I rerplaced original plastic hose with insulated acustic duct. Now it's better.
This spring, I was trying to use it as a heater...but, the duct should be repositioned In/Out to make heat.
I also have a fixed watercooled Flagship AC - I think 16000btu. This "Made with pride!" unit is noisy like a bear,blows charts out of the table but, have troubles to cool.The reason maybe the water isn't cold,or that the pump runs on 50Hz instead of 60Hz - 20% waterflow. And, not able to start with my Panda. Only with 32 Amps/220V,or 50Amps/110V shore.
I'm about to go for the 3-d unit - to cool the aft cabins - I have a place to locate it with a short,direct ducting to the cabins. And , Dometic Turbo DTU 16 looks right (about $3K offers) ,plus the Smart Start. But, I have a fear to drop another $3K++ without any positive signs... Maybe othe CFM have used Slef Contained AC units?

If it is noisy and blows the charts off the table then you do not have enough static pressure in the vents. It is not the unit itself that is noisy but the air itself. Also with no static or back pressure the air has no time to cool before it moves on. You need to put 240 GPH through the unit to get the proper cooling on the condenser.

[a64pilot]

Originally Posted by Scout 30

What I'd like to know is what's the biggest marine ac unit that can be run by a Honda 2000? We were talking to a Rosborough dealer recently & he was installing the Coleman 9500 btu roof units because the Honda 2000 was able to run them.

You can run a decently efficient 16K one with the Dometic smart start, but not a chance without one, usually. Some get by, but it's not guaranteed. I installed a hard start Cap on mine and it helped a little bit, but nothing like the Dometic Smart start, but I guess you get what you pay for.

My old Honda would run my 6K with no problem at all on eco mode, but 6K just isn't a lot of cooling. Interestingly the 6K pulls about half the current the 16K does, but about 1/3 the cooling. Both are Webasto, en economy AC.

Oh and a Honda running a 16K AC is working hard, and it sounds like it too

[Scout 30]

Originally Posted by a64pilot

You can run a decently efficient 16K one with the Dometic smart start, but not a chance without one, usually. Some get by, but it's not guaranteed. I installed a hard start Cap on mine and it helped a little bit, but nothing like the Dometic Smart start, but I guess you get what you pay for.

My old Honda would run my 6K with no problem at all on eco mode, but 6K just isn't a lot of cooling. Interestingly the 6K pulls about half the current the 16K does, but about 1/3 the cooling. Both are Webasto, en economy AC.

Oh and a Honda running a 16K AC is working hard, and it sounds like it too

Thanks! Exactly the info I was looking for.

[YARGESOL]

Originally Posted by Outlaw7

If it is noisy and blows the charts off the table then you do not have enough static pressure in the vents. It is not the unit itself that is noisy but the air itself. Also with no static or back pressure the air has no time to cool before it moves on. You need to put 240 GPH through the unit to get the proper cooling on the condenser.

Outlaw7, I could increase static pressure,installing choks in the ducts.Cooling pump is March LC-3CP-MD,it flows 8,5gpm,even if it works 20%slower with 50Hz current,it's way over 240GPH. Should I try to upgrade it to 14GPM,or stay with what I have and manage vents? I'm not going to dismiss this system.But,in any case it's built for the front cabs+salon. For the aft Master/Admiral cab I need another AC

[Outlaw7]

Yes you can try obstructing the vents there now. That unit works best with 4 4 inch vents or the equivalent of 50 square inches of outlet. It also wants to see 140 square inches of return air. How big is the inlet and outlet you have now? Also to big of a duct with no back pressure can pull moisture off the evaporator causing high humidity or a cold clammy boat. What is the cubic footage of the area you are trying to cool? And how many square feet of non vertical windows?

[YARGESOL]

Originally Posted by Outlaw7

Yes you can try obstructing the vents there now. That unit works best with 4 4 inch vents or the equivalent of 50 square inches of outlet. It also wants to see 140 square inches of return air. How big is the inlet and outlet you have now? Also to big of a duct with no back pressure can pull moisture off the evaporator causing high humidity or a cold clammy boat. What is the cubic footage of the area you are trying to cool? And how many square feet of non vertical windows?

I'm trying to cool approx 1800 cub.ft and I have approx 18 sq.ft of non-vertical windows & hatches. I'm replacing acriliyc glass now and will cover it with Armolan film,reducing the sun heat to 5%. Not sure about the inlet - this syistem was built with the prvious owner.I think, that the blower take the air from the equipment room itself - means,where the AC is located,together with the watermaker and the step down trafo. All the visible ducts goes to the salon/cabin with the cooled air. Will be on the boat next week and will check

[Outlaw7]

Wow,
If you use the calculator of 1800 X 16 as shown on their sight you will see that it says you need 28,800 BTU Add in the windows at 200 btu per square foot that adds another 3,600 BTU. Your unit is grossly undersized for the area it needs to cover. Also if the unit is not in the area it's to serve and if the return air is not directly ducted to the unit and if the area it's installed in is not well sealed and if it is in a machinery area that has equipment running adding to the heat load that too will cause problems. Sounds to me like blaming the unit is not really fair to it.

[YARGESOL]

I know,that something was made wrong and I'm trying to save this system. I may disconnect the front cabs (they have exellent ventilation with the hatches and portlights) and circle the air inside salon. But,the OP is wondering about 2x12000 btu units,for his prospective cat. My cat is not the biggest one and,this Flagship unit is set to cool 2/3 of my 46 cat, Portable 14000btu unit is doing well (just the salon).What I'm missing are the aft cabins,the most important for us.I can't direct the duct from Flagship (too far).Most likely will bite for Dometic
Turbo 16 +the Smart Start

[a64pilot]

I'm just a 38' mono with small port lights with UV film and the hatches covered with insulated covers.
Boat had originally one 16 K unit, and that would not cool the boat, I eliminated all but one large very short as in 1' run of duct and added a 6K to our Stateroom and left the aft Stateroom un airconditioned, and in the S Fl heat, the two ACs just barely do it.
With your larger Cat, you likely need the cooling that Outlaw is suggesting.
If you end up with a little extra than you need, then you can run them on low and enjoy the lack of noise, too little and of course it never quite gets cool.